Zavada et al., International Publication Number WO 93/18152 (published 16 Sep. 1993) and U.S. Pat. No. 5,387,676 (issued Feb. 7, 1995), describe the discovery and biological and molecular nature of the MN gene and protein. The MN gene was found to be present in the chromosomal DNA of all vertebrates tested, and its expression to be strongly correlated with tumorigenicity.
The MN protein was first identified in HeLa cells, derived from a human carcinoma of cervix uteri. It is found in many types of human carcinomas (notably uterine cervical, ovarian, endometrial, renal, bladder, breast, colorectal, lung, esophageal, and prostate, among others). Very few normal tissues have been found to express MN protein to any significant degree. Those MN-expressing normal tissues include the human gastric mucosa and gallbladder epithelium, and some other normal tissues of the alimentary tract. Paradoxically, MN gene expression has been found to be lost or reduced in carcinomas and other preneoplastic/neoplastic diseases in some tissues that normally express MN, e.g., gastric mucosa.
In general, oncogenesis may be signified by the abnormal expression of MN protein. For example, oncogenesis may be signified: (1) when MN protein is present in a tissue which normally does not express MN protein to any significant degree; (2) when MN protein is absent from a tissue that normally expresses it; (3) when MN gene expression is at a significantly increased level, or at a significantly reduced level from that normally expressed in a tissue; or (4) when MN protein is expressed in an abnormal location within a cell.
Zavada et al., WO 93/18152 and Zavada et al., WO 95/34650 (published 21 Dec. 1995) disclose how the discovery of the MN gene and protein and the strong association of MN gene expression and tumorigenicity led to the creation of methods that are both diagnostic/prognostic and therapeutic for cancer and precancerous conditions. Methods and compositions were provided therein for identifying the onset and presence of neoplastic disease by detecting or detecting and quantitating abnormal MN gene expression in vertebrates. Abnormal MN gene expression can be detected or detected and quantitated by a variety of conventional assays in vertebrate samples, for example, by immunoassays using MN-specific antibodies to detect or detect and quantitate MN antigen, by hybridization assays or by PCR assays, such as RT-PCR, using MN nucleic acids, such as, MN cDNA, to detect or detect and quantitate MN nucleic acids, such as, MN mRNA.
Zavada et al, WO 93/18152 and WO 95/34650 describe the production of MN-specific antibodies. A representative and preferred MN-specific antibody, the monoclonal antibody M75 (Mab M75), was deposited at the American Type Culture Collection (ATCC) in Manassus, Va. (USA) under ATCC Number HB 11128. The M75 antibody was used to discover and identify the MN protein and can be used to identify readily MN antigen in Western blots, in radioimmunoassays and immunohistochemically, for example, in tissue samples that are fresh, frozen, or formalin-, alcohol-, acetone- or otherwise fixed and/or paraffin-embedded and deparaffinized. Another representative and preferred MN-specific antibody, Mab MN12, is secreted by the hybridoma MN 12.2.2, which was deposited at the ATCC under the designation HB 11647. Example 1 of Zavada et al., WO 95/34650 provides representative results from immunohistochemical staining of tissues using MAb M75, which results support the designation of the MN gene as an oncogene.
Many studies have confirmed the diagnostic/prognostic utility of MN. The following articles discuss the use of the MN-specific MAb M75 in diagnosing/prognosing precancerous and cancerous cervical lesions: Leff, D. N., “Half a Century of HeLa Cells: Transatlantic Antigen Enhances Reliability of Cervical Cancer Pap Test, Clinical Trials Pending,” BioWorld® Today: The Daily Biotechnology Newspaper, 9(55) (Mar. 24, 1998); Stanbridge, E. J., “Cervical marker can help resolve ambigous Pap smears,” Diagnostics Intelligence. 10(5): 11 (1998); Liao and Stanbridge, “Expression of the MN Antigen in Cervical Papanicolaou Smears Is an Early Diagnostic Biomarker of Cervical Dysplasia,” Cancer Epidemiology. Biomarkers & Prevention, 5: 549-557 (1996); Brewer et al., “A Study of Biomarkers in Cervical Carcinoma and Clinical Correlation of the Novel Biomarker MN,” Gynecologic Oncology, 63: 337-344 (1996); and Liao et al., “Identification of the MN Antigen as a Diagnostic Biomarker of Cervical Intraepithelial Squamous and Glandular Neoplasia and Cervical Carcinomas,” American Journal of Pathology, 145(3): 598-609 (1994).
Premalignant and Malignant Colorectal Lesions. MN has been detected in normal gastric, intestinal, and biliary mucosa. [Pastorekova et al., Gastroenterology, 112: 398-408 (1997).] Immunohistochemical analysis of the normal large intestine revealed moderate staining in the proximal colon, with the reaction becoming weaker distally. The staining was confined to the basolateral surfaces of the crystal epithelial cells, the area of greatest proliferative capacity. As MN is much more abundant in the proliferating cryptal epithelium than in the upper part of the mucosa, it may play a role in control of the proliferation and differentiation of intestinal epithelial cells. Cell proliferation increases abnormally in premalignant and malignant lesions of the colorectal epithelium, and therefore, is considered an indicator of colorectal tumor progression. [Risio, M., J. Cell Biochem. 16G: 79-87 (1992); and Moss et al., Gastroenterology. 111: 1425-1432 (1996).]
The MN protein is now considered to be the first tumor-associated carbonic anhydrase (CA) isoenzyme that has been described. Carbonic anhydrases (CAs) form a large family of genes encoding zinc metalloenzymes of great physiological importance. As catalysts of reversible hydration of carbon dioxide, these enzymes participate in a variety of biological processes, including respiration, calcification, acid-base balance, bone resorption, formation of aqueous humor, cerebrospinal fluid, saliva and gastric acid [reviewed in Dodgson et al., The Carbonic Anhydrases, Plenum Press, New York-London, pp. 398 (1991)]. CAs are widely distributed in different living organisms.
In mammals, at least seven isoenzymes (CA I-VII) and a few CA-related proteins (CARP/CA VIII, RPTP-β, RPTP-τ) had been identified [Hewett-Emmett and Tashian, Mol. Phyl. Evol., 5: 50-77 (1996)], when analysis of the MN deduced amino acid sequence revealed a striking homology between the central part of the MN protein and carbonic anhydrases, with the conserved zinc-binding site as well as the enzyme's active center. Then MN protein was found to bind zinc and to have CA activity. Based on that data, the MN protein is now considered to be the ninth carbonic anhydrase isoenzyme—MN/CA IX. [Opavsky et al., Genomics. 33: 480-487 (May 1996)]. [See also, Hewett-Emmett, supra, wherein CA IX is suggested as a nomenclatural designation.]
CAs and CA-related proteins show extensive diversity in both their tissue distribution and in their putative or established biological functions [Tashian, R. E., Adv. in Genetics, 30: 321-356 (1992)]. Some of the CAs are expressed in almost all tissues (CA II), while the expression of others appears to be more restricted (CA VI and CA VII in salivary glands). In cells, they may reside in the cytoplasm (CA I, CA II, CA III, and CA VII), in mitochondria (CA V), in secretory granules (CA VI), or they may associate with membrane (CA IV). Occasionally, nuclear localization of some isoenzymes has been noted [Parkkila et al., Gut, 35: 646-650 (1994); Parkkilla et al., Histochem. J. 27: 133-138 (1995); Mori et al., Gastroenterol., 105: 820-826 (1993)].
The CAs and CA-related proteins also differ in kinetic properties and susceptibility to inhibitors [Sly and Hu, Annu. Rev. Biochem., 64: 375-401 (1995)]. In the alimentary tract, carbonic anhydrase activity is involved in many important functions, such as saliva secretion, production of gastric acid, pancreatic juice and bile, intestinal water and ion transport, fatty acid uptake and biogenesis in the liver. At least seven CA isoenzymes have been demonstrated in different regions of the alimentary tract. However, biochemical, histochemical and immunocytochemical studies have revealed a considerable heterogeneity in their levels and distribution [Swensen, E. R., “Distribution and functions of carbonic anhydrase in the gastrointestinal tract,” In: The Carbonic Anhydrases. Cellular Physiology and Molecular Genetics, (Dodgson et al. eds.) Plenum Press, New York, pages 265-287 (1991); and Parkkila and Parkkila, Scan J. Gastroenterol. 31: 305-317 (1996)]. While CA II is found along the entire alimentary canal, CA IV is linked to the lower gastrointestinal tract, CA I, III and V are present in only a few tissues, and the expression of CA VI and VII is restricted to salivary glands [Parkkila et al., Gut, 35: 646-650 (1994); Fleming et al., J. Clin. Invest., 96: 2907-2913 (1995); Parkkila et al., Hepatology. 24: 104 (1996)].
MN/CA IX has a number of properties that distinguish it from other known CA isoenzymes and evince its relevance to oncogenesis. Those properties include its density dependent expression in cell culture (e.g., HeLa cells), its correlation with the tumorigenic phenotype of somatic cell hybrids between HeLa and normal human fibroblasts, its close association with several human carcinomas and its absence from corresponding normal tissues [e.g., Zavada et al., Int. J. Cancer, 54: 268-274 (1993); Pastorekova et al., Virology, 187: 620-626 (1992); Liao et al., Am. J. Pathol. 145: 598-609 (1994); Pastorek et al., Oncogene, 9: 2788-2888 (1994); Cote, Women's Health Weekly: News Section, p. 7 (Mar. 30, 1998); Liao et al., Cancer Res., 57: 2827 (1997); Vermylen et al., “Expression of the MN antigen as a biomarker of lung carcinoma and associated precancerous conditions,” Proceedings AACR. 39: 334 (1998); McKiernan et al., Cancer Res. 57: 2362 (1997); and Turner et al., Hum. Pathol., 28(6): 740 (1997)]. In addition, the in vitro transformation potential of MN/CA IX cDNA has been demonstrated in NIH 3T3 fibroblasts [Pastorek et al., id.].
The MN protein has also been identified with the G250 antigen. Uemura et al., “Expression of Tumor-Associated Antigen MN/G250 in Urologic Carcinoma: Potential Therapeutic Target,” J. Urol., 157 (4 Suppl.): 377 (Abstract 1475; 1997) states: “Sequence analysis and database searching revealed that G250 antigen is identical to MN, a human tumor-associated antigen identified in cervical carcinoma (Pastorek et al., 1994).”
MN/CA IX has been identified as a novel hypoxia regulated marker in invasive breast cancer as reported in Chia et al., “Prognostic Significance of a Novel Hypoxia Regulated Marker, Carbonic Anhydrase IX (MN/CAIX) in Invasive Breast Cancer,” Breast Cancer Research and Treatment, 64(1): 43 (November 2000). Chia et al. stated “that MN/CA IX expression is significantly increased in hypoxic conditions across various cell lines.” MN/CA IX expression was “found to be significantly associated with a higher tumor grade (p=0.003), a negative estrogen receptor status (P<0.001) and tumor necrosis (p<0.001) . . . associated with significantly worst relapse-free survival (p=0.004) and a worse overall survival (p=0.001).”
Hypoxia is a reduction in the normal level of tissue oxygen tension. It occurs during acute and chronic vascular disease, pulmonary disease and cancer, and produces cell death if prolonged. Pathways that are regulated by hypoxia include angiogenesis, glycolysis, growth-factor signaling, immortalization, genetic instability, tissue invasion and metastasis, apoptosis and pH regulation. [Harris, A. L., Nature Reviews, 2: 38-47 (January 2002).]
Tumors become hypoxic because new blood vessels that develop in the tumors are aberrant and have poor blood flow. Although hypoxia is toxic to both tumor cells and normal cells, tumor cells undergo genetic and adaptive changes that allow them to survive and even proliferate in a hypoxic environment. These processes contribute to the malignant phenotype and to aggressive tumor behavior. Hypoxia is associated with resistance to radiation therapy and chemotherapy, but is also associated with poor outcome regardless of treatment modality, indicating that it might be an important therapeutic target. Additionally, there is a need to find an alternative to the current Eppendorf pO2 histograph method for assessing tumor hypoxia in patients. Although the Eppendorf method provides prognostic information in a variety of tumor types, it is limited to tumors acceptable for microneedle insertion. [Harris, A. L., id.]
The central mediator of transcriptional up-regulation of a number of genes during hypoxia is the transcription factor HIF-1. HIF-1 is a heterodimer that consists of the hypoxic response factor HIF-1α and the constitutively expressed aryl hydrocarbon receptor nuclear translocator (ARNT, also known as HIF-1β). In the absence of oxygen, HIF-1 binds to HIF-binding sites within hypoxia-response elements (HREs) of oxygen-regulated genes, thereby activating the expression of numerous hypoxia-response genes, such as erythropoietin (EPO), and the proangiogenic growth factor vascular endothelial growth factor (VEGF).
Semenza et al. PNAS (USA), 88: 5680-5684 (1991) first identified cis-activating DNA sequences that function as tissue-specific hypoxia-inducible enhancers of human erythropoietin expression. Pugh et al., PNAS (USA), 88: 10533-71 (1991) isolated such a DNA sequence 3′ to the mouse erythropoietin gene which acts as a hypoxia-inducible enhancer for a variety of heterologous promoters. Maxwell et al., PNAS (USA), 90: 2423-2427 (1993) have shown that the oxygen-sensing system which controls erythropoietin expression is widespread in mammalian cells.
McBurney et al., Nucleic Acids Res., 19: 5755-61 (1991) found that repeating the hypoxia response element (HRE) sequence, located 5′ to the hypoxia-inducible mouse phosphoglycerate kinase gene (PGK), leads to increased induction of the gene, and that using the interleukin-2 gene under tissue-specific promoters can be used for specific targeting of tumors.
Hypoxia can be used to activate therapeutic gene delivery to specific areas of tissue. Dachs et al. “Targeting gene expression to hypoxic tumor cells,” Nat. Med., 3: 515-20 (1997) has used the HRE from the mouse PGK gene promoter to drive expression of heterologous genes both in vitro and in vivo with controlled hypoxia.
For some HIF targets such as VEGF, a clear function in promoting tumor growth is established. [Kim et al., “Inhibition of vascular endothelial growth factor-induced angiogenesis suppresses tumour growth in vivo,” Nature (Lond.), 362: 841-844 (1993).] However, the full range of HIF target genes has not yet been defined, and identification of additional genes responding to this pathway is likely to provide further insights into the consequences of tumor hypoxia and HIF activation.
Indirect support for the importance of microenvironmental activation of HIF has also been provided by recent demonstrations of constitutive activation of HIF after inactivation of the VHL tumor suppressor gene. [Maxwell et al., “The tumour suppressor protein VHL targets hypoxia-inducible factors for oxygen-dependent proteolysis,” Nature (Lond.), 399: 271-275 (1999)] and amplification of the HIF response by other oncogenic mutations. [Jiang et al., “V-SRC induces expression of hypoxia-inducible factor 1 (HIF-1) and transcription of genes encoding vascular endothelial growth factor and enolase 1: involvement of HIF-1 in tumor progression,” Cancer Res. 57: 5328-5335 (1997); Blagosklonny et al., “p53 inhibits hypoxia-inducible factor-stimulated transcription,” J. Biol. Chem., 273: 11995-11998 (1998); Ravi et al., “Regulation of tumor angiogenesis by p53-induced degradation of hypoxia-inducible factor 1α,” Genes Dev., 14: 34-44 (2000); Zundel et al., “Loss of PTEN facilitates HIF-1 mediated gene expression,” Genes Dev., 14: 391-396 (2000).]
Mutations in VHL cause the familial syndrome and are also found in the majority of sporadic RCCs. [Gnarra et al., “Mutations of the VHL tumour suppressor gene in renal carcinoma,” Nat. Genet. 7: 85-90 (1994).] The gene product pVHL forms part of ubiquitin-ligase complex, [Lisztwan et al., “The von Hippel-Landau tumor suppressor protein is a component of an E3 ubiquitin-protein ligase activity,” Genes Dev. 13: 1822-1833 (1999); Iwai et al., “Identification of the von Hippel-Lindau tumor-suppressor protein as part of an active E3 ubiquitin ligase complex,” Proc. Natl. Acad. Sci. (USA) 96: 12436-12441 (1999)] that targets HIF-α subunits for oxygen-dependent proteolysis. [Maxwell et al., (1999) supra; Cockman et al., “Hypoxia inducible factor-α binding and ubiquitination by the von Hippel-Landau tumor suppressor protein,” J. Biol. Chem., 275: 25733-25741 (2000).]
In VHL-defective cells, HIF-α is stabilized constitutively, resulting in up-regulation of hypoxia-inducible genes such as VEGF. [Maxwell et al., (1999) supra.] Although the pVHL ubiquitinligase complex may have other targets [Iwai et al., supra] and other functions of pVHL have been proposed that may contribute to tumor suppressor effects [Pause et al., “The von Hippel-Lindau tumor suppressor gene is required for cell cycle exit on serum withdrawal,” Proc. Natl. Acad. Sci. (USA) 95: 993-998 (1998); Ohh et al., “The von Hippel-Landau tumor suppressor protein is required for proper assembly of an extracellular fibronectin matrix,” Mol. Cell, 1: 959-968 (1998)], these recent findings raise important questions as to the range of genes affected by constitutive HIF activation and role of such genes in oncogenesis.
In that respect, MN/CA 9 considered to be an oncogene has an interesting position as a transmembrane carbonic anhydrase (CA). CAs catalyze the reversible hydration of carbon dioxide to carbonic acid [Sly et al., Annu. Rev. Biochem. 64: 375-401 (1995)], providing a potential link between metabolism and pH regulation. One aspect of this invention is the relationship between MN/CA 9 and hypoxia. MN/CA IX is shown to be one of the most strongly hypoxia-inducible proteins.